1. Field of the Invention
This invention relates to decking or shelving used primarily in industrial and commercial racks for storing goods and articles.
2. Description of the Related Art
Decking or shelving used in industrial and commercial storage racks has to be designed and constructed to bear heavy loads without twisting or buckling. For example, shelving used in bulk storage applications must be able to support the weight of densely packed rows of boxes filled with goods. In such applications, a solid steel sheet deck would be an ideal choice for shelving because it has a high load-bearing capacity.
The design and construction of decking or shelving must comply, however, with the requirements of any fire codes applicable to the particular storage environment. Fire codes generally require that the surface area of each deck or shelf have a certain amount of open area, e.g., a number of holes distributed along the surface of the deck or shelf. Obviously, a solid steel sheet deck would not meet this xe2x80x9copen areaxe2x80x9d requirement and therefore could not be used as storage rack shelving.
The xe2x80x9copen areaxe2x80x9d requirement serves two primary objectives from the standpoint of fire safety and prevention. First, the open area of each deck or shelf allows a fire that has broken out to move vertically up the storage rack instead of spreading horizontally to other storage racks, as the fire would do if it had broken out beneath a solid steel sheet deck. It also allows heat generated by the fire to dissipate instead of building up within a semi-enclosed space, as would be the case in a storage space between two solid steel sheet decks. In short, the open area creates a flue space within a storage rack, thereby causing the fire to travel upward and to release heat in the process. This maximizes the effectiveness of the sprinkler system in containing the fire because it allows the fire to reach the sprinkler heads as quickly as possible without building up too much heat and intensity.
Second, the open area of each deck or shelf allows water from an overhead sprinkler system to flow downward in the event of a fire. As long as water runs freely through the individual decks or shelves, an overhead sprinkler system can adequately contain a fire breaking out at any shelving level and prevent it from spreading to other storage racks.
The amount of open area generally required by fire codes is fifty percent (50%) of the surface area. Lower percentages may be allowed, however, depending on the particular storage environment. As pointed out above, a solid steel sheet deck does not have any open area and therefore would not meet this xe2x80x9cfifty-percentxe2x80x9d rule. Consequently, it could not be used in bulk storage applications even though it has a high load-bearing capacity.
The fifty-percent rule necessarily calls for a unique solution to the problem of providing structural strength to decking or shelving. Solutions currently available in the industry are simply inadequate.
For example, a wire mesh deck, commonly used in industrial and commercial settings, meets the fifty-percent rule but it deforms relatively easily under heavy loads because it has no uniform loading support. When it deforms, the deck no longer has a flat surface on which to rest boxes. It is difficult enough, even with a flat surface, to load boxes onto a wire mesh deck and to move them from side to side once they are on the deck. The loss of a flat surface further aggravates this problem.
Moreover, a wire mesh deck tends to rip up bulk items, thereby damaging stored goods. Cardboard boxes, carpets, and upholstered goods are susceptible to damage from punctures and snags as they are loaded onto or off a wire mesh deck. A wire mesh deck also creates a safety risk because the wire ends along the so-called xe2x80x9cwaterfallxe2x80x9d edge that hugs the support beam can bend up and cut a worker""s stray finger or other body part.
Wire mesh decks require long lead times for production. They cannot be packed densely in shipping, and therefore the costs of shipping are higher than they otherwise could be.
A slatted wooden deck, also commonly used, has disadvantages of its own. Wood burns and smokes readily. It also warps and moves due to moisture and has to be replaced more often than steel. Obviously, wooden decks are not as strong as steel decks, and the individual slats may break, thereby causing a failure in the structural integrity of the deck and a safety hazard for workers.
Another bulk storage solution is a rollformed xe2x80x9cfront to back bar.xe2x80x9d This solution consists of a rollformed C-channel with welded end plates that attach to a step beam. This solution is very expensive from a manufacturing standpoint because it uses a lot of heavy gauge steel. Moreover, one still has to use wooden pallets because the solution itself does not provide a flat storage surface.
Recognizing the disadvantages inherent in wire mesh decks and slatted wooden decks, and the need for decking or shelving that meets fire code requirements without sacrificing load-bearing capacity, others besides the present inventors have experimented with alternative designs and constructions. Consider the following examples.
U.S. Pat. No. 5,199,582 to Halstrick discloses storage rack shelving in which there are corrugated decks with channels below the top surface for guiding and confining sprinkler fluid. Evenly spaced along the channels are openings through which sprinkler fluid flows down to the next shelving level. The decks, however, each have an open area of less than one-half of 1% of the total deck area. This obviously would not meet the fifty-percent rule.
Indeed, Halstrick""s invention expressly teaches away from the use of open decking. The disclosure of U.S. Pat. No. 5,199,582 considers open decking to be undesirable because it allows hot air to flow upward and cause a chimney effect. The disclosure points out that Halstrick""s invention does not permit smoke and gas to flow upwardly.
Contrary to this disclosure and as explained above, open decking actually works together with an overhead sprinkler system to contain a fire. Here is the chain of events that occur when a fire breaks out in a storage environment. The fire""s natural tendency is to rise, seeking out additional oxygen. Smoke and hot air also rise. They thus find their way to the closest sprinkler head, which activates and releases a spray of water. The water falls downward, thereby containing the fire and protecting areas adjacent to where the fire started. The open decking also allows excess heat to dissipate more rapidly. This is important because a hotter fire will be more difficult for the sprinkler system to contain, as the water droplets vaporize before they make contact with the flames.
U.S. Pat. No. 3,986,462 to Heft discloses shelving units with circular holes uniformly spaced throughout the surface area to permit the passage of water. Each shelving unit derives its structural strength through the presence of side members depending from the longitudinal edges of the top portion. Each shelf in turn is made up of several shelving units placed side by side on the beams of the rack. One apparent disadvantage with this design is the fact that the shelving units must be precisely sized so that they interlock snugly with the rack beams.
Another disadvantage of Heft""s invention is that the units would be prohibitively expensive to manufacture because of the high cost of materials. The units would also be costly to ship and install. Additionally, the circular holes in the shelving units weaken the structure such that the design cannot bear heavy loads. The holes also turn the shelving units into cheese graters that can damage stored goods and injure people.
U.S. Pat. No. 3,927,769 to Maslow et al. discloses a shelf made of a rectangular sheet of material having raised ribs to support items placed thereon and apertures to permit the flow of air or water. The ribs reinforce the shelf structure. Based on the drawings accompanying this patent, however, it does not appear that this design would meet the fifty-percent rule generally required by fire codes today.
Despite alternative designs and constructions that have been proposed over the years, as exemplified by the above patents, wire mesh decks and slotted wooden decks are still widely used in industrial and commercial storage racks. There have been few attempts to address the needs of industry for decking and shelving that meets the fifty-percent rule and yet provides the load-bearing capacity required in bulk storage applications. Such decking or shelving should also be nonflammable and suitable for mass production and shipping at minimal cost.
The invention described below fulfills all of the above objectives. It offers a simple and elegant solution to industry requirements of shelving having up to fifty-percent open area and a structure designed to withstand maximum stress with minimum amount of deflection. This invention provides a smooth flat surface for storage of bulk items. Moreover, in the preferred embodiments, this solution can be readily implemented with minimal retooling of existing machines for fabricating metals and manufactured and shipped at competitive prices.
Decking or shelving made according to the present invention consists of corrugated decks having a plurality of apertures punched or formed into the horizontal surface areas according to a predetermined pattern that specifies the shape, size and frequency of the apertures. The apertures are punched or formed so that a downwardly sloping, vertical flange surrounding each aperture is created. Each flange directs the flow of liquid from the adjacent horizontal surface area of the corrugated deck into the aperture. Each flange also reinforces the structural integrity of the deck, making it suitable for high load-bearing applications. In the preferred embodiments, the corrugated decks are made from galvanized sheet steel, but other materials such as plastics and fiberglass can also be used.